In a gas turbine, steam turbine, and the like, turbine stationary blades and turbine rotating blades are arranged in a pathway along which a fluid (combustion gas or vapor) flows. The stationary blades are supported by a member on a fixed side such as a casing, and the turbine rotating blades are supported by a member on a rotating side such as a rotating shaft.
Turbine blades, including the turbine stationary blade and the turbine rotating blade, may be provided with a through-hole connecting the surface of the turbine blade to an interior space thereof. The through-hole is, for example, a film cooling hole performing film cooling of the turbine blade by discharging cooling air from the interior.
Various methods have been proposed as a method to form the through-hole in the turbine blade (a turbine blade machining method) (refer to Patent Documents 1 and 2). For example, Patent Document 1 discloses a method including applying a bond coating to a blade base material, drilling film cooling holes, forming a top coat, and removing the top coat of a region including a row of the cooling holes by air blasting or water jet. Furthermore, Patent Document 2 discloses a method including applying a thermal barrier coating to metal components of a gas turbine engine having a cooling hole formed of a metering hole, a cooling hole outlet, and a trough part, and removing the coating adhering to the metering hole first by water jet or laser and then removing the coating adhering to the cooling hole outlet and removing finally the coating of the trough part.